Solvent refining of wax-containing mixtures



Sept. 14, 1954 E, w CLARKE 2,689,206

SOL-VENT REFINING OF WAX-CONTINING MIXTURES Filed Feb. 25, 1951 wax .5) :roc/r A Y A. 42'2'231' INVENTOR.

Patented Sept. 14, 1954 SOLVENT REFINING F WAX-CONTAINING MIXTURES Edgar W. Clarke, Laurel Springs, N. J., assignor to The Atlantic Refining Company, Philadelphia, Pa., a corporation of Pennsylvania Application February 23, 1951, Serial No. 212,289

The portion of the term of the patent subsequent to JulyV 17, 1968, has been disclaimed and dedicated to the public 2 Claims.

The present invention relates to the treatment of oily waxes, and more particularly to the separation of wax-containing mixtures into fractions of higher and lower melting point.

This invention is especially applicable to the deoiling of hydrocarbon waxes containing not more than 70% of oil, and to the separation of wax mixtures of low oil content into fractions of different melting point.

This'application is a continuation-in-part of copending application Serial No. 779,922, led October 15, 1947, now U. S. Patent No. 2,561,696, and entitled Solvent Refining of Wax-Containing Mixtures.

In accordance with the invention, a Wax-containing mixture is separated into fractions of higher and lower melting point by admixing the wax-containing mixture with pyridine as the selective solvent at a temperature above the cloud point of the admixture, cooling the admixture to a temperature below the cloud point such that two immiscible liquid phases are formed, one phase comprising a major portion of the higher melting Wax in the form of finely divided particles suspended in a minor portion of the sol-A vent, and the second phase comprising a major portion of the solvent containing dissolved lower melting wax, oil, and color bodies, separating the phases from one another, and removing the solvent vfrom each. The quantity of solvent em-t ployed will usually range from 3 to 5 volumes per volume of wax-containing mixture to be treated, although in some cases as little as 1.5 volumes of solvent may be used. The cloud point will depend upon the nature of the wax-containing mixture, as well as upon the composition and volume of solvent used. The temperature of the initial heating must be above the cloud point, and may be above the miscibility temperature of the admixture. The cooling is preferably carried to a temperature between 1 F. and 5 F, below the cloud point, in order that the higher melting wax may crystallize and form a suspension of iinely divided particles in the immiscible liquid phase.

This suspension is characterized as being nonlterable due to the neness of the particles, but

applied in the refining, purification, or separation of wax stocks such as petroleum slack Wax, crude microcrystalline wax, parafiin waxes, petrolatum wax, montan wax, ceresin, ozokerite, waxes from the distructive or non-destructive hydrogenation of mineral oil, synthetic hydrocarbon oil, shale oil, coal, and waxes produced synthetically by the catalytic reaction of hydrocarbons, or waxes derived from the modified Fischer-Tropsch reaction of carbon monoxide and hydrogen.

The present invention may be further understood with reference to the accompanying drawing which represents diagrammatically a Z-Stage system suitable for carrying out the process.

Referring to the drawing, the wax stock in a molten condition is delivered from a storage vessel l through valve-controlled pipe v2 to pipe 3 surrounded by a heating jacket 4 through which steam or other medium may be circulated to maintain the desired temperature. A hot solvent extract, pyridine, containing lower melting wax,

oil, and possibly color bodies, is simultaneously supplied to` pipe 3 through pipe 5, the source of such solvent extract being described in detail hereinafter. In passing through jacketed pipe 3, the temperature of the Wax stock and solvent extract is adjusted to a value above the cloud point of the admixture, and if desired, such temperature may be raised toor above the miscibility temperature of the admixture. The cloud point may be considered that temperature at which the higher melting wax appears as a suspension of finely divided solid particles, such particles being substantially non-lterable. In general, the temperature of the admixture at this stage should be from 5 F. to 30 F. above -the cloud point. The admixture, at a temperature above its cloud point, is thoroughly agitated in its passage through pump 6, and is delivered by such pump to a cooling coil l or other suitable device for decreasing the temperature. Coil 'I is surrounded by jacket 8 through which brine, water, or other cooling medium may be circulated. In passing through Coil l, the temperature .of the admixtureis reduced to a value be- This mixture is passed from coil l through valvecontrolled pipe 9 into settling vessel llll provided with a rotatable stirrer Il, which, if desired, may

,be described. .from the bottom of tower I3 and passedby valve- ,34. `through pipe 35, condensed in condenser 36, and` also function as a scraping device for loosening wax which may adhere to the walls of the vessel. In vessel I0, the mixture is permitted to settle and stratify into two layers, the upper layer comprising for the most part the higher melting'wax particles and a minor amount of solvent, for example, 5% to 20% by volume of the upper` layer. The lower layer comprisesy the major 'portion' of the solvent in which is dissolved the lower melting wax, oil, and color bodies (if present). A small amount of finely divided Yhigher ymelting wax particles may also be entrained in thelower layer, due to failure to pass upwardly from the extract solution into the upper layer comprising the higher melting wax particles. .The lower layer is then drawn from settling vessel Ifand is passed through valve-controlled pipe I2 into a fractionating or stripping tower I3 provided with a heating coil M. In tower I3, the solvent is removed from the lower melting wax by vaporization, the solvent vapors being taken overhead through pipe I5, condensed in condenser I6, and delivered by valve-controlled pipe l1 to lvalve-controlled pipe IS for further use, as will The lower melting Wax-is drawn controlled pipe I9 into storage vessel 20.

The upper layer contained in settling vessel I0,

comprising the major portion of the higher melting wax in the form of nely divided particles suspended in a minor portion Iof the solvent, is slowly agitated by rotation of stirrer II,

.and is drawn from vessel I through valve-con- `trolled pipe IB and is commingled therein with solvent from valve-controlled pipe I'I, as well as vwith solvent delivered by valve-controlled pipe ,.2I, the source of which will be hereinafter described. The resulting admixture of nely divided higher melting wax and solvent is passed through pipe 22 surrounded by heating jacket 23, and the temperature of the admixture is brought to a value above the cloud point, and vif desired, above the miscibility temperature. The heated mixture is then delivered by pump 24, with thorough agitation, to cooling coil 25 surrounded by jacket 26 through which a cooling medium may be circulated. The temperature of themixture is reduced to a level a few degrees below its cloud point (1 F. to 5 FJ, and the mixture is then delivered by valve-controlled pipe 21 to settling vessel 28 provided with stirrer 29. Herein, the immiscible liquid phases `are permitted to settle and stratify, and there is produced an upper layer comprising a major portion of the higher melting wax in the form of a ne `suspension in a minor amount of solvent, the

wax being relatively light colored and of much reduced oil content. The lower layer comprises the major portion of the solvent with minor amounts of lower melting wax, oil, and color bodies, if present. The lower layer is withdrawn from vessel 28 and is recycled by means of valvecontrolled pipe to pipe 3 for use as explained hereinbefore.

The upper layer contained in vessel 28 is slowly agitated by stirrer 29, and is passed by valvecontrolled pipe 30 to the fractionating or stripping tower 3l, provided with heating coil 32. In tower 3 I, the solvent is separated from the higher melting wax by distillation, the wax being withdrawn from the bottom of the tower via valvecontrolled pipe 33 and passed to storage vessel 'Ihe solvent is taken overhead .as vapor delivered by valve-controlled pipe 2| to pipe I8 for further use as described hereinbefore.

While the invention has been particularly de- -scribed with respect to the operation ofa 2-stage system, it is obvious that it may likewise be carried out in a system of any desired number of f stages, depending upon the degree of separation of the wax-containing mixture required. Preference is had for a system containing from 3 to 5 stages in order to obbtain the most effective separation of the higher and lower melting point 'WafXeS.

The present invention may be further illustrated by thefollowing examples, which, however, are not to be construed as limiting the scope thereof.

'(1) A ,slack wax of brown color having e. melting point of 113 F. and an oil content of 41.3% by weight was extracted with pyridine in a three-stage system `operated in the manner described with reference to the system'shown in the drawing. The volume ratio of .pyridinento wax stock was 4.5 to 1 and the extraction temperature in the rst stage was F. and yin the second-and third stages F. In the table .which follows, a comparison is made between the :properties of the charge stock together withvthe properties of the raffinate and extract phases from the process.

(le Remnant Extract Percent Yield by Weight... 35.7 64.3. Melting Point, F 1131...... 1321...... 102.4. Percent Oil Content by 41.3....... 2...-. :49.8.

Weight. Refractive Index at 176 F.. 1.44l5 1.4298... 1 4496. Color Bro\vn. White Flrniness Nil Good Tackiness Poor .do o Plasticity.... Too soft..- Moderate.. rloo soft Fiber Length Short..... Long Short. Flexibility Poor Moderate..

(llge Raffinate Extract Percent Yield by Welght.. 100 11 l 88.9. Melting Point, F 113.1.. 110.7. Percent Oil Content by 24.2. 22.9.

Weight. Refractive Index at 176 F.... l.43525.... 1.43402-.-- 1.43500. Color Brown.... White... Brown.

I claim:

l. The method of separating a wax-containing mixture into fractions of higher and lower melting point, which comprises admixing .said wax-containing mixture with from 3 to 5 volumes of pyridine at a temperature above thecloud lpoint of the admixture, cooling the admixture to a temperature of 1 F. to 5 F. below thecloud point such that two immiscible yliquid phases .are formed, one phase comprising a major,portion of the higher melting wax in the form -offmely divided, unlterable particles suspended in .a minor portion of the pyridine,.and.the.vsecond phase comprising a major portion .of thepyridine containing dissolved lower melting wax, oil and color bodies, separating the phases from one another, and removing the pyridine from each.

2. The method of separating a wax-containing mixture into fractions of higher and lower melting point, which comprises admixing said Waxcontaining mixture with from 3 to 5 volumes of pyridine at a temperature of 5 F. to 30 F. above the cloud point of the admixture, cooling the admixture to a temperature of 1 F. to 5 F. below the cloud point such that two immiscible liquid phases are formed, one phase comprising a major portion of the higher melting wax in the form of finely divided, unlterable particles suspended in a minor portion of the pyridine, and the second phase comprising a major portion of 6 the pyridine containing dissolved lower melting Wax, oil, and color bodies, separating the phases from one another, and removing the pyridine from each.

References Cited in the i'lle of this patent UNITED STATES PATENTS Number Name Date 10 2,017,432 Bahlke Oct. 15, 1935 2,063,369 Diggs et al. Dec. 8, 1936 2,126,493 McKittrick et al. Aug. 9, 1938 2,191,136 Tijmstra Feb. 20, 1940 2,302,434 Dons et a1. Nov. 17, 1942 15 2,561,096 Clarke July 17, 1951 

1. THE METHOD OF SEPARATING A WAX-CONTAINING MIXTURE INTO FRACTIONS OF HIGHER AND LOWER MELTING POINT, WHICH COMPRISES ADMIXING SAID WAX-CONTAINING MIXTURE WITH FROM 3 TO 5 COLUMES OF PYRIDINE AT A TEMPERATURE ABOVE THE CLOUD POINT OF THE ADMIXTURE, COOLING THE ADMIXTURE TO A TEMPERATURE OF 1* F. TO 5* F. BELOW THE CLOUD POINT SUCH THAT TWO IMMISCIBLE LIQUID PHASES ARE FORMED, ONE PHASE COMPRISING A MAJOR PORTION OF THE HIGHER MELTING WAX IN THE FORM OF FINELY DIVIDED, UNFILTERABLE PARTICLES SUSPENDED IN A MINOR PORTION OF THE PYRIDINE, AND THE SECOND PHASE COMPRISING A MAJOR PORTION OF THE PYRIDINE CONTAINING DISSOLVED LOWER MELTING WAX, OIL AND 